(1) Field of the Invention
The present invention relates to methods and apparatus for developing or otherwise treating substrates such as semiconductor wafers, glass substrates for liquid crystal displays, glass substrates for photomasks, and substrates for optical disks. More particularly, the invention relates to a technique of performing a predetermined treatment of substrates by supplying a developer or other treating solution to the substrates in a spin.
(2) Description of the Related Art
A conventional substrate treating apparatus will be described, taking a developing apparatus for example.
FIG. 1 is a view in vertical section of a developer discharge nozzle in a conventional substrate developing apparatus. FIG. 2 is a section taken on line A--A of FIG. 1.
A developer discharge nozzle 100 shown in FIGS. 1 and 2 has a cylindrical nozzle body 100a with a closed bottom. The nozzle body 100a has a plurality of (five in this example) discharge openings 101 (first to fifth discharge openings 101a-101e) formed equidistantly in the circumferential surface thereof A developer supply pipe 102 is connected to an upper surface of nozzle body 100a.
To perform developing treatment of a wafer W with a developer supplied from the nozzle 100 having the above construction, the nozzle 100 is moved to position the first discharge opening 101a over the spin center P of wafer W as shown in FIG. 3, for example. Then, the developer is supplied (as at Q in FIG. 1) while spinning the wafer W. The developer delivered from the nozzle 100 having the discharge openings 101 formed laterally thereof makes only a mild impact on a film coated and exposed on the surface of wafer W. On the other hand, as depicted in concentric circles drawn in two-dot chain lines in FIG. 3, the developer discharged concentrates on and adjacent regions under the second and fifth discharge openings 101b and 101e equidistant from the spin center P, and on and adjacent regions under the third and fourth discharge openings 101c and 101d equidistant from the spin center P. With the concentration of the highly active developer, development progresses faster in the regions along these concentric circles than in the other regions. This results in the problem of impairing uniformity of development over the wafer surface.
To avoid the inconvenience due to the developer concentration in the form of concentric circles, the nozzle 100 is moved radially of the wafer W while supplying the developer to the spinning wafer W.
However, such conventional practice has the following drawback.
When the nozzle 100 is moved over the spinning wafer W, each of the discharge openings 101a-101e of nozzle 100 describes a spiraling locus as shown in a solid line in FIG. 3. The second and fifth discharge openings 101b and 101e equidistant from the spin center P describe similar loci close to each other. The third and fourth discharge openings 101c and 101d equidistant from the spin center P also describe similar loci close to each other. As a result, the developer concentrates along the pairs of loci close to each other, which provides no significant improvement in the uniformity of development.
The above nozzle 100 has the following disadvantages also.
Because of the very construction of nozzle 100, air 103 inevitably collects in an upper space of the nozzle body 100a. When the developer is supplied to the nozzle body 100a through the supply pipe 102, the air 103 in the upper space of the nozzle body 100a is compressed by the flow pressure. The air 103 then expands in reaction thereto. This results in an unsteady discharge of the developer from the discharge openings 101.
Moreover, the air 103 collecting in the upper space of the nozzle body 100a may mix into the developer in the nozzle body 100a. The developer may contain bubbles when supplied from the discharge openings 101 to the upper surface of wafer W. Then, as shown in FIG. 4, the developer Q fails to contact the upper surface of wafer W where bubbles 104 contact the upper surface of wafer W. This causes local defects in development.
Further, when stopping supply of the developer Q to the wafer W, it is conventional practice to stop supplying the developer Q to the nozzle body 100a through the supply pipe 102, leaving the developer Q in the nozzle body 100a as shown in FIG. 5. As noted above, when the developer Q is supplied to the nozzle body 100a through the supply pipe 102, the air 103 in the upper space of the nozzle body 100a is compressed by the flow pressure. The pressure of developer Q acting on the air 103 is eliminated when the developer Q is stopped being supplied to the nozzle body 100a through the supply pipe 102. Then, the air 103 expands as shown in a two-dot chain line in FIG. 5, which causes the developer Q to drip from the nozzle body 100a to the wafer W, thereby jeopardizing uniform treatment.